Hi,

I would suggest looking into the platform ports:

https://trustedfirmware-a.readthedocs.io/en/latest/plat/arm/fvp/fvp-specific-configs.html#booting-a-kernel-image-in-bl33

https://trustedfirmware-a.readthedocs.io/en/latest/plat/rpi3.html#build-instructions RPI3_DIRECT_LINUX_BOOT

https://trustedfirmware-a.readthedocs.io/en/latest/plat/qemu.html#qemu-virt-armv8-a ARM_LINUX_KERNEL_AS_BL33

Regards,

Olivier.

From: Joita Mitra <joita.m@delopt.co.in>
Sent: 11 June 2026 09:19
To: tf-a-owner@lists.trustedfirmware.org <tf-a-owner@lists.trustedfirmware.org>
Subject: Guidance on direct Linux boot from TF-A (bypassing U-Boot) on ARM64

Hi,

I am working on an RZ/G2L based platform and exploring the possibility of booting Linux directly from TF-A without using U-Boot as BL33.

Current boot flow:

BL2 -> BL31 -> U-Boot (BL33) -> Linux

Target boot flow:

BL2 -> BL31 -> Linux

I have been studying the TF-A image loading framework, including:

desc_image_load.h
bl2_image_load_v2.c
bl2_plat_mem_params_desc.c
bl31_main.c
bl31_prepare_next_image_entry()

My understanding is that BL2 loads images according to the image descriptors and passes entry point information to BL31 through the BL33 descriptor.

I modified the BL33 descriptor to point to the Linux kernel entry address instead of U-Boot and attempted to transfer execution directly to Linux from BL31.

However, Linux does not start successfully, which suggests that additional preparation normally performed by U-Boot may be missing.

I would appreciate guidance on the following:

Is using the BL33 descriptor to describe the Linux kernel the correct architectural approach when bypassing U-Boot?
How should the Linux kernel Image and DTB be loaded from BL2?

Should Linux be treated as BL33?
Should the DTB be loaded as a separate image descriptor?
Is there an existing TF-A mechanism intended for this use case?

Which TF-A components are typically modified to support direct Linux boot?

BL2 image loading descriptors?
BL31 handoff logic?
Platform-specific image loading code?

Are there any reference implementations or platforms in TF-A that directly boot Linux without U-Boot?
Are there any ARM64 Linux boot protocol requirements that TF-A must satisfy before transferring control to Linux?

Any guidance or examples would be greatly appreciated.

Thank you.

Joita Mitra

Embedded Software Engineer

+91-7985313796

Fortune Serene, 3rd Floor, Plot No: 89/B, 90/A, West Avenue 9, Electronic City Phase 1,Bangalore 560100